|Gene:||UXS3||Accession Number: AT5G59290 (MetaCyc)|
Synonyms: At5g59290, UDP-xylose synthase
Species: Arabidopsis thaliana col
The Nicotiana tabacum UXS3 gene encodes a protein (AtUXS3) with UDP-glucuronate decarboxylase activity [Harper02], involved in the conversion of UDP-glucuronate into UDP-xylose. Unlike AtUXS1 and AtUXS2, this enzyme does not possess a hydrophobic N-terminal domain thought to anchor the protein in endomembranes; the C-terminus moiety of the protein supposedly faces the lumen of endomembrane compartments [Harper02]. AtUXS3 has a very high substrate specificity for UDP-GlcA. UDP-glucose, UDP-galactose, UDP-mannose, GDP-glucose, GDP-mannose and UDP-galacturonate were not used as substrates [Harper02]. This enzyme does not require exogenously added NAD+, although the cofactor is required for activity. Moreover, the addition of NADH, NADPH or NADP+ failed to inhibit the activity of AtUXS3. It is therefore thought that NAD+ is tightly bound to the protein [Harper02]. AtUXS3 has a broad pH range (pH 4.5 to 9.5) but is completely inactive at pH values below 3.2 (interestingly, at this pH, preincubation of the enzyme with NAD+ retains 60% of enzyme activity [Harper02]). In addition, the enzyme also displays a broad temperature range: 22?C to 42?C. No activity was detected beyond 55?C.
Molecular Weight of Polypeptide: 38.5 kD (from nucleotide sequence)
Unification Links: ArrayExpress:Q9FIE8 , Entrez:AAK70882 , ModBase:Q9FIE8 , PhylomeDB:Q9FIE8 , Pride:Q9FIE8 , Protein Model Portal:Q9FIE8 , SMR:Q9FIE8 , String:3702.AT5G59290.2-P , Swiss-Model:Q9FIE8 , TAIR:At5g59290 , UniProt:Q9FIE8
|Cellular Component:||GO:0005829 - cytosol [Pattathil05]|
Enzymatic reaction of: UDP-glucuronate decarboxylase
EC Number: 18.104.22.168
The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the Enzyme Commission system.
The reaction is favored in the direction shown.
T(opt): 30 °C [Harper02]
pH(opt): 5.5 [Harper02]
Harper02: Harper AD, Bar-Peled M (2002). "Biosynthesis of UDP-xylose. Cloning and characterization of a novel Arabidopsis gene family, UXS, encoding soluble and putative membrane-bound UDP-glucuronic acid decarboxylase isoforms." Plant Physiol 130(4);2188-98. PMID: 12481102
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